1. Field of the Invention
The present invention relates to a method of bonding a tubulation tubing of a display panel, more particularly, a method of bonding a tubulation tubing to a display panel such as a plasma display panel (PDP) for removing an impurity gas from an electric discharge space in the display panel and introducing an electric discharge gas into the discharge space.
2. Description of Related Art
In a display panel such as a PDP, the discharge space is usually formed in the panel by disposing a front substrate and a back substrate of the panel opposedly and sealing the peripheries of the substrates together. Typically, in the production of the panel, a vent hole is opened in the back substrate and a glass tubulation tubing is bonded to the perimeter of the vent hole when the front and back substrates are sealed together. Via this tubulation tubing, the impurity gas is removed from the inside of the panel and the discharge gas is fed in the panel. Thereafter, the tubulation tubing is cut by fusing (melting) so that a tubulation path in the tubulation tubing is closed, thereby making the discharge space air-tight.
In order to bond the tubulation tubing to the back substrate, usually, a glass frit or glass powder is mixed with a binder and formed in a ring shape. This glass material (also referred to as a sealing glass) is preliminarily baked to release gas therefrom and placed between a flare edge of the tubulation tubing and the back substrate. The glass material is fastened provisionally with the tubulation tubing by means of a clip. Thereafter a sealing step is conducted for sealing the front substrate and the back substrate together (by fusing a sealing member with heat), thereby also welding the tubulation tubing to the back substrate with the glass material.
However, since the glass material is between the flare end portion of the tubulation tubing and the back substrate, the glass material, melted, may enter the inside of the tubulation tubing and block the tubulation tubing when the tubulation tubing and the back substrate are bonded by melting the glass material. The melted glass material may also enter the inside of the panel when the impurity gas is vented out and the discharge gas is fed into the panel.
Where the sealing step is carried out after the glass material has been provisionally fastened together with the tubulation tubing by a clip, the glass material softened in the sealing step is pushed out from between the flare end portion of the tubulation tubing and the back substrate and adheres to the clip. As a result, it may become difficult to remove the glass material when the clip is taken off or the glass material may crack when removed.
Further, if the pressing force by the clip for holding the tubulation tubing is too strong, the glass member is pushed out from the flare end portion of the tubulation tubing. For this reason, the pressing force cannot be strengthened above a certain degree. Therefore, when the sealing step is carried out with the glass material being provisionally fastened together with the tubulation tubing by the clip, the tubulation tubing may possibly be inclined when a little force is applied.